Construction materials referred to as MMC materials have become known during the latest decade. The MMC materials are composites formed from a binder material such as aluminum, titanium or alloys from these with a reinforcement by admixture of fibers or particles from substances such as silicon carbide, boron carbide or aluminum oxide. Typically, the reinforcement content is about 15% by weight to about 70% by weight of the MMC material.
MMC materials have very interesting properties, which may be tailored depending upon the field of use, whereby achieving advantages such as making a component lighter, stronger, more rigid and providing the component with better endurance properties than what is possible to achieve by using conventional materials within the specific field of use.
Vehicle technology where fast moving parts, such as piston rods, suitably could be performed by means of these metal composites is an example of a field of use for MMC materials. Vehicle manufacturers constantly try to attain increasing performance with respect to fuel consumption, emissions, vibrations, noise, comfort and the like. Essential with respect to all of these parameters is decreased weight, especially in non-resilient mass and in fast moving engine parts. Especially within competition activities where motor vehicles are used, the above mentioned properties for engine parts are very desirable. Piston rods represent, as mentioned, an example of such components where decreased weight is very favorable.
Within racing activities for vehicles light materials such as aluminum, titanium or coal fiber composites are generally used instead of steel for the mentioned types of is components.
Another interesting field of use for MMC products is brake discs for cars, trucks and trains.
One major drawback when using MMC material is that the material has been very hard to machine. When shaping a component employing a MMC material, methods such as casting the component in a mold which closely corresponds to the finally completed shape of the component are applied. Another method is to use a forged work piece or a portion of an extruded rod, whereby spark-machining of the surface of the component and conventional machining may be used to arrive at the final shape of the component. Attempts have been made to produce, by example, piston rods for motorbikes by using conventional manufacturing machining methods. Hereby, the purpose of arriving at the desired component with its desired properties, such as lower weight, has been achieved. The use of such a piston rod in an engine has given as a result an engine which more willingly moves into a higher gear and further induces lower vibrations to the engine. The problem is, however, that the costs for manufacturing the engine part are very high, which imply that the use is restricted or limited to fields where the costs are of minor importance.
A number of patent documents disclose different methods for a final stage shaping of components made by MMC materials. U.S. Pat. No. 5,765,667 is here mentioned as one example. This patent describes a method for manufacturing a component, in this example a disc brake, by means of casting the component to a shape which very closely corresponds to the final shape of the component, in order to, and this is distinctly expressed, as far as possible avoid the need for machining by cutting tools. It is obvious for the person skilled in the art to avoid the need for machining by cutting tools, as the MMC material, when it is composed of an aluminum base and reinforcement in the form of silicon carbide particles contains exactly the composition which is generally used for grinding cutting tools.
The silicon particles embedded in the MMC material have a devastating effect on the cutting tools when machining by the use of conventional machining technique, as the edges of the cutting tools rapidly are worn out by the grinding particles within the composite material.
The present invention discloses an unexpected solution to the above-described problem.